Sintered metal fiber liner for gas burners

ABSTRACT

An improved liner for gas burners used to confine combustion in a compact zone adjacent the burner face is formed of a porous sheet of sintered metal fibers. The novel liner features uniform flow therethrough of air and provides improved insulation in that the escape of heat from the combustion zone through the liner is curtailed. Structural simplicity is another advantage of the new liner.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a liner for gas burners. More particularly, the invention provides a liner for gas burners used to maintain combustion in a compact zone while permitting the flow of air along the outer side of the liner as well as through the liner into the combustion zone. Liners are especially used with gas burners of gas turbines.

[0002] Metal liners for gas burners have long been used particularly in the operation of gas turbines. For example, U.S. Pat. No. 4,311,447 to Rackley et al shows a metal liner surrounding a radiant surface combustor, the term commonly used in lieu of gas burner by the gas turbine industry. U.S. Pat. No. 6,199,364 to Kendall et al discloses not only several burners with individual metal liners but also several burners within a pair of liners. Metal liners frequently have multiple openings so that air flowing along the outer surface also enters the combustion zone confined by the liner. U.S. Pat. No. 6,453,672 of Kendall et al illustrates two types of metal liners: a louvered liner and a backside-cooled liner. The prior art indicates that a consensus has not been reached regarding the best metal liner.

[0003] A principal object of this invention is to provide an entirely new type of liner for gas burners (combustors).

[0004] Another important object is to provide liners of simple form that permit the flow of air substantially uniformally through all of the surface of the liners.

SUMMARY OF THE INVENTION

[0005] Basically, the liner of the invention is formed of a porous sheet of sintered metal fibers that are resistant to the temperature and oxidizing conditions of the combustion zone confined by the liner.

[0006] U.S. Pat. No. 5,326,631 to Carswell discloses that fibers made of an iron-based or nickel-based alloy containing chromium are suitable for exposure to the conditions of the combustion zone. U.S. Pat. No. 4,597,734 to McCausland et al mentions an alloy containing iron chromium and aluminum.

[0007] The porous sheet of sintered metal fibers is formed by initially laying a fiber pad from an air or liquid dispersion of the fibers. The fiber pad is then mechanically compressed, usually by rolling, into a dense but porous sheet that is finally sintered.

[0008] If greater porosity is desired in some portions of the liner of this invention, the porous sheet of sintered metal fibers used to form the liner may have perforated areas. U.S. Pat. No. 5,439,372 to Duret et al teaches such porous sheets of sintered metal fibers having dual porosities.

[0009] The porous sintered metal fiber liner of this invention may be provided with a reinforcing metal backing in the form of a perforated metal sheet. Such reinforcement makes it possible to minimize the thickness of the porous sintered metal fiber liner and thus replace costly alloy fibers with common sheet metal. Preferably, the porous metal fiber liner is sintered to the perforated sheet metal used as reinforcement. Preferably, the perforations in the reinforcing metal sheet occupy at least 80% of the area of the sheet. Most preferably, the perforations of the reinforcing metal sheet occupy about 95% of the area of the sheet. The reinforced liner of the invention is used with the metal fiber side directly exposed to the combustion confined by the liner.

[0010] Another way of economizing on the alloy fibers that are exposed to combustion involves forming the porous fiber liner as two layers: one layer of inexpensive metal fibers and another layer of metal fibers selected for resistance to combustion conditions. The latter layer would face the combustion zone. The two fiber layers would be compressed into a unitary sheet and sintered to yield the porous fiber liner of this invention.

[0011] The porous sheet of sintered metal fibers used to form a liner for combustors achieves a uniformity of air flow therethrough into the combustion zone not attained by any prior liner. In addition to this advantage, the sintered metal fiber liner provides a better insulating effect against heat flow from the combustion zone. A metal sheet of the same thickness as a porous sheet of sintered metal fibers is a much better heat conductor; in short, the porosity of sintered metal fibers acts as insulation.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0012] As an example of the invention, a 2 millimeter thick porous sheet of sintered metal fibers purchased from N.V. Acotech S.A. of Zwevegem, Belgium, is bent and shaped as a liner. The edges of the porous sheet that are abutted to close the liner are spot-welded together to complete the simple formation of the novel liner. The portion of this liner near the exit end of the combustion zone is preferably perforated, similar to the manner shown in the aforementioned Duret et al patent, to increase the flow of air into the hot gases leaving the combustion zone. Perforations with diameters of about 0.050 to 0.075 inch are generally preferred.

[0013] Those skilled in the art will visualize variations and modifications of the invention in light of the foregoing teachings without departing from the spirit or scope of the invention. Accordingly, only such limitations should be imposed on the invention as are set forth in the appended claims. 

What is claimed is:
 1. A combustor liner comprising a porous sheet of sintered metal fibers which faces and confines combustion from a combustor.
 2. The combustor liner of claim 1 wherein the porous sheet of sintered metal fibers is bonded to a perforated metal sheet, the perforations of which cover at least 80% of the area of said sheet.
 3. The combustor liner of claim 1 wherein the metal fibers are fibers of an alloy selected from the group consisting of iron-based or nickel-based alloys containing chromium, and alloys containing iron, chromium and aluminum.
 4. The combustor liner of claim 1 wherein the portion of the liner near its exit end is perforated.
 5. The combustor liner of claim 1 wherein the porous sheet of sintered metal fibers is formed of two layers of fibers of different metal compositions.
 6. The combustor liner of claim 5 wherein one layer of fibers have a metal composition selected from the group consisting of iron-based or nickel-based alloys containing chromium, and alloys containing iron, chromium and aluminum.
 7. The combustor liner of claim 3 wherein the porous sheet of sintered metal fibers is bonded to a perforated metal sheet, the perforations of which cover about 95% of the area of said sheet.
 8. The combustor liner of claim 4 wherein the porous sheet of sintered metal fibers is about 2 millimeters thick.
 9. The combustor liner of claim 8 wherein the portion of the liner near its exit end is perforated. 